The present invention relates to a method for protecting data recorded on a partial read-only memory (ROM) medium from unauthorized copying, and more particularly, to a method for preventing generation of "third generation data" of an original data recorded on the partial ROM medium.
In this specification, a "read-write region" refers to a region of a data recording medium in which recording and reproduction can be performed.
A "read-only" region refers to a region of a data recording medium in which only reproduction can be performed.
In this specification, "partial ROM medium" refers to a data recording medium having both a read-write region and a read-only region. The partial ROM medium includes partial ROM optical disks. The structure of a partial ROM optical disk is described below.
A "read-only medium" refers to a data recording medium having only a read-only region.
A "read-write medium" refers to a data recording medium having only a read-write region. "First generation data" refers to data recorded on an original medium. Typically, the first generation data is released from a software developer.
"Second generation data" refers to data produced by copying the first generation data from the original medium to a second medium.
"Third generation data" refers to data produced by copying the second generation data from the second medium to a third medium.
A first conventional technique for preventing the generation of the third generation data is disclosed in Japanese Unexamined Patent Publication No. 82039/1992.
In the first conventional technique, an overwriting data is overwritten onto the copy source data prior to copying the copy source data. If the copy source data is first generation data recorded on a read-only medium, the overwriting operation does not destroy the copy source data. On the other hand, if the copy source data is the second generation data recorded on a read-write medium, the copy source data is destroyed by the overwriting data. This selective destruction allows the generation of the second generation data, but prevents the generation of the third generation data.
A second conventional technique for preventing the execution of second generation program data is disclosed in Japanese Unexamined Patent Publication No. 356760/1992. In the second conventional technique, a pass-word which cannot be copied by the copy operation is recorded on an original disk. A program is executed after confirming that the predetermined pass-word is recorded along with the program. That is, the program cannot be executed without the original disk.
However, the aforementioned conventional techniques have the following problems.
For example, in the first conventional technique, the copy operation cannot be prevented when the copy source medium is set in a write-protect state. When the copy source medium is set in the write-protect state, the overwriting data is not overwritten on the copy source data. Therefore, the copy source data on a read-write medium (second generation data) is not destroyed and third generation data is generated.
The problem can be solved by providing a medium-state determining means. In this improvement, the state of the disk is determined prior to the overwriting operation. If the copy source medium is set in the write-protect state, the copy operation is inhibited. According to this method, the copy operation is permitted only when the copy source medium is set in the write-enable state.
However, this improvement also has a problem that the improvement requires a special storage device with the medium state determining means.
The second conventional technique also has a problem in that the original disk is easily damaged because the original disk is frequently subjected to the read operation.